The nanoscale science and engineering have shown great promise for the fabrication of novel biosensors with faster response and higher sensitivity than that of planar sensor configurations, due to their small dimensions combined with a dramatically increased contact surface and strong binding with biological and chemical reagents. Such biosensors have important applications in medicine, in biological and biochemical research, as well as for environmental monitoring and protection and in food industry.
In the last few years nanoparticle technology has been used to build chemical sensors and biosensors for detecting various analytes from contaminants in air to the presence of particular DNA segments in blood and other samples.
Encapsulated metal nanoparticles could be functionalized with different kind of ligands to give a chemical sensor that uses changes in the electrical characteristics of the metal nanoparticle and thus could function as an electronic nose for gas phase or electronic tongue for liquid phase as described for example in the US 2005/0142030.
In addition the WO 2004/086044 discloses that silver nanoparticles or gold nanoparticles could serve as nanosensors in one or the other way if appropriately sized and functionalized. However, to take full advantage of the physical characteristics of small sized particles such as for localized surface plasmon resonance (LSPR) spectroscopy as detection method, these particles need to have even size and physical characteristics and/or need to be even geometrically organized on substrates.
Another limitation of metal nanoparticles as described in the above mentioned documents is their production via wet chemical synthesis. This type of production disables the precise control on size and shape of the particle and does not permit even immobilization of particles on substrates.
More recently, chemical and biosensors utilizing nanotubes such as single- or multi-walled carbon nanotubes have been proposed. Such sensors were produced using conventional semiconductor fabrication techniques to give non-horizontal or horizontal orientated nanotubes or -wires on solid surfaces as described in WO 2005/031299 or in WO 2005/093831. However, conventional semiconductor fabrication techniques do not allow the geometric organization of nanostructures on solid surfaces as lithographic techniques do.
Lithography as technique for the production of nanostructured surfaces exist in various types. One type of lithography is electron beam lithography and has been used for example in FR 2 860 872 to create a distribution of circular or ellipsoidal “plots” on a two dimensional surface, or to it. A great disadvantage of this technique is that it is very cost-intensive.
Electrodeposition of nanoparticles on nanotubes or wires as described in US 2005/0157445 gives miniaturized electrical devices but need conductive elements.
The publications and other materials, including patents, used herein to illustrate the invention and, in particular, to provide additional details respecting the practice are incorporated herein by reference. For convenience, the publications are referenced in the following text by numerals in brackets and are listed accordingly in the appended bibliography.